The present invention relates to methods, apparatus, and systems for low-flow sampling of a fluid source.
The present invention relates to a well and groundwater sampling. Wells are used in the environmental and water supply industries, among other things, to collect samples of groundwater for chemical analysis. A typical well, shown in FIG. 1, is comprised of a slotted section of pipe 37 (the xe2x80x9cwell screenxe2x80x9d) located at the bottom of the well, a well point 39 which plugs the bottom of well screen 37 and sections of solid pipe 41 (the xe2x80x9criser pipexe2x80x9d) which thread onto well screen 37 and each other to bring the well to a ground surface 49. The slots in well screen 37 are narrow enough (e.g., on the order of hundredths of an inch) to keep out soil particles, but allow in groundwater. The water level within a well having a portion of well screen 37 above a water table 43 (e.g., water table well 45) is the same as the level of water table 43 since atmospheric pressure alone is acting equally on both. If the entire well screen is located beneath water table 43 (e.g., in deep well 47), additional pressures, such as the weight of the water above, act on the groundwater. The pressures acting on a unit measure of groundwater are referred to as xe2x80x9chead pressure.xe2x80x9d Groundwater will flow from areas of high head pressure to areas of low head pressure. Groundwater entering deep well 47 will usually flow upward into riser pipe 41 until it reaches equilibrium. The water level at equilibrium is sometimes referred to as the piezometric surface.
Since the water in a water table well is exposed to the atmosphere, it is not considered representative of groundwater outside the well screen. In a deep well, as a result of the water flowing into riser pipe 41 until equilibrium is reached, standing water may be present in the riser pipe between groundwater sampling events. This water may be present for weeks, months, or longer, and is also not considered representative of the groundwater outside of the well screen. In conventional systems, up to six volumes of standing water must be purged from the well. The purged water typically needs to be treated to remove contaminants before it can be discharged, which may require costly and time-intensive off-site treatment.
One illustrative embodiment of the invention is directed to a method for manually sampling a fluid source in a well, comprising an act of exerting a downward pressure on a sample tube, disposed within a well insert, to allow fluid to pass from the well through a portion of the well insert and into the sample tube to fill at least a portion of the sample tube with the fluid.
Another illustrative embodiment of the invention is directed to a method for securing a well insert to an inner wall of a well, comprising acts of arranging stabilizers on the well insert in a non-extended position; introducing the well insert into the well; arranging the stabilizers on the well insert in an extended position; and expanding a portion of a gasket on the well insert such that the portion of the gasket conforms to a circumference of the inner wall of the well.
A further illustrative embodiment of the invention is directed to an apparatus, comprising a well insert including a piston, the well insert being mounted to an inner surface of a well; and a sample tube, with means for activating the piston, disposed within the well insert.
Another illustrative embodiment of the invention is directed to an apparatus, comprising a well insert for insertion into a well; stabilizers mounted to the well insert, the stabilizers being movable from a non-extended position to an extended position such that when the stabilizers are in an extended position, the stabilizers extend to a location at or beyond a diameter of an inner wall of the well; and a gasket mounted to the well insert, the gasket being radially extendable from a non-extended position to an extended position such that when the gasket is in an extended position, the gasket conforms to a circumference of the inner wall of the well.